Exercise

Distributed Systems Fundamentals: Check Your Understanding

Five questions covering the CAP theorem, consistency models, and the resilience and messaging patterns from this learning path.

1. During a network partition, the CAP theorem forces a distributed system to choose between which two guarantees?

Consistency and AvailabilityConsistency and Partition ToleranceAvailability and Partition ToleranceNone — all three can always be guaranteed

2. What guarantee does an eventually consistent system actually provide?

Every read immediately returns the most recent writeIf no new updates are made, all replicas will eventually converge to the same valueWrites are rejected outright during any partitionConsistency is guaranteed, but only for the client that performed the write

3. Which state does a circuit breaker enter to stop sending requests to a failing downstream service?

ClosedHalf-openOpenPaused

4. How does the Saga pattern keep data consistent across services without a two-phase commit?

By locking every resource involved until the whole transaction completesBy running a sequence of local transactions, with compensating actions to undo prior steps if a later step failsBy retrying failed steps forever without ever rolling backBy requiring every service to share one physical database

5. What problem does the Outbox pattern solve?

It replaces the need for a message broker entirelyIt guarantees exactly-once delivery with no deduplication needed downstreamIt guarantees at-least-once event delivery by writing the event in the same database transaction as the business data changeIt prevents duplicate messages purely through network-level retries

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